A dermatome is an area of skin supplied by a particular spinal nerve. When you lose feeling in particular areas of skin, the loss of function can be linked to these spinal nerves. For instance, numbness on the pinky (medial) side of your arm in the area h

Pupillary dilation is regulated by a descending pathway from the hypothalamus. The pathway courses through the lateral part of the brain stem, to the sympathetic preganglionic neurons in the first three segments of the thoracic intermediolateral cell column. These cells project to the superior cervical ganglion from which sympathetic axons run along the carotid artery to the orbit, where they innervate the pupillodilator muscle in the iris.